Field of the Invention
The present invention relates to an organic light emitting display apparatus, and more particularly, to an organic light emitting display apparatus with improved reliability and a manufacturing method thereof.
Discussion of the Related Art
Recent transition into an information-oriented society has caused rapid development in the field of displays to visually represent electrical information signals. Correspondingly, a variety of flat panel display apparatuses exhibiting excellent properties, such as thin profile, light weight and low power consumption, have been developed.
Representative examples of these flat panel display apparatuses may include liquid crystal display (LCD) apparatuses, plasma display panel (PDP) apparatuses, field emission display (FED) apparatuses, electro luminescence display (ELD) apparatuses, electro-wetting display (EWD) apparatuses, and organic light emitting display (OLED) apparatuses.
All of the aforementioned flat panel display apparatuses essentially include a flat display panel to display an image. The flat display panel is fabricated by bonding a pair of substrates to face each other with an inherent light emitting material or a polarizer interposed therebetween, and includes a display face defined by a display region and a peripheral non-display region around the display region. The display region is defined by a plurality of pixel areas.
Among the flat panel display apparatuses, organic light emitting display apparatuses are configured to display an image using self-illuminating organic light emitting devices. That is, the organic light emitting display apparatuses include a plurality of organic light emitting devices corresponding to a plurality of pixel areas.
Typically, such an organic light emitting device includes first and second electrodes arranged facing each other, and an organic layer formed of an organic material between the first and second electrodes to attain electro-luminescence based on a drive current between the first and second electrodes.
One of the first and second electrodes (hereinafter referred to as “first electrode”) corresponds to each pixel area, and the other (hereinafter referred to as “second electrode”) corresponds to all of the pixel areas in common.
The second electrode is formed in a wide area to correspond to all of the pixel areas, and thus has a higher resistance than that of the first electrode. In particular, when the organic light emitting display apparatus is a top emission type, light is emitted through the second electrode. Therefore, the second electrode may be formed of a transparent conductive material that is as thin as possible to maintain light emission efficiency, i.e., brightness of each pixel area, thereby having higher resistance.
The higher resistance of the second electrode, however, causes a greater voltage drop (IR drop, I: electrical current, R: electrical resistance), and therefore the respective pixel areas may have different brightness based on a distance from a power source. That is, the high resistance of the second electrode deteriorates brightness uniformity throughout the pixel areas. In addition, the high resistance of the second electrode increases power consumption of the organic light emitting display apparatus for acquisition of brightness over a critical value, despite the voltage drop.
In particular, as the area of the organic light emitting display apparatus increases, deterioration of brightness uniformity and increase of power consumption due to the high resistance of the second electrode are worsened, which restricts increase in the area of the organic light emitting display apparatus.
To solve the above described problems, a general organic light emitting display apparatus may further include a bus electrode formed of a lower resistance material than the second electrode and connected to the second electrode, to reduce a resistance of the second electrode.
In this case, the bus electrode is disposed facing the second electrode, and an organic layer is interposed between the bus electrode and the second electrode. Thus, for connection of the second electrode and the bus electrode, at least a portion of the bus electrode must be exposed without formation of the organic layer thereon.
In one example, to expose at least a portion of the bus electrode, selective etching of the organic layer may be contemplated. However, this etching may cause damage to the entire organic layer and leave an etched organic material with impurities, thereby resulting in deterioration in the reliability of the organic light emitting display apparatus.